The EPS of the 3rd Generation Partnership Project (“3GPP” for short) is constituted by an Evolved Universal Terrestrial Radio Access Network (“E-UTRAN” for short), a Mobility Management Entity (“MME” for short), a Serving Gateway (“S-GW” for short), a Packet Data Network GateWay (“P-GW” for short), a Home Subscriber Server (“HSS” for short), a 3GPP AAA server (3GPP Authorization/Authentication/Accounting server), a Policy and Charging Rules Function (“PCRF” for short) and other supporting nodes, wherein the S-GW is an access gateway equipment connected with the E-UTRAN for forwarding data between the E-UTRAN and the P-GW and responsible for buffering paging waiting data; the P-GW is a boarder gateway between the EPS and a Packet Data Network (“PDN” for short) and is responsible for the access of the PDN and for forwarding data between the EPS and the PDN, etc.; the PCRF obtains service information via a Rx interface and a operator Internet Protocol (“IP” for short) service network interface, and is connected with the gateway equipment in the network via a Gx/Gxa/Gxc interface, is responsible for initiating establishment of an IP bearer, ensures Quality of Service (“QoS” for short) of the service data, and controls the charging.
The EPS supports the interworking with a non-3GPP network. The interworking between the EPS and the non-3GPP network is realized via an S2a/b/c interface. The P-GW is used as an anchor point between the 3GPP network and the non-3GPP network. The non-3GPP network comprises: trusted non-3GPP network and untrusted non-3GPP network, wherein the IP access of the trusted non-3GPP network may be directly interfaced with P-GW via the S2a; and the IP access of the untrusted non-3GPP network needs be connected with the P-GW through an Evolved Packet Data Gateway (“ePDG” for short) with the S2b as the interface between the ePDG and the P-GW.
In the 3GPP network between the EPSs, a Policy and charging enforcement function (“PCEF” for short) exists in the P-GW. All functions can be controlled as long as the PCRF is connected with the P-GW. The PCRF exchanges information with the P-GW via the Gx interface. When the interface between the P-GW and the S-GW is based on Proxy Mobile IP (“PMIP” for short), a Bearer Binding and Event Report Function (“BBERF” for short) is present in the S-GW, and the S-GW exchanges information with the PCRF via the Gxc interface. When the trusted non-3GPP network accesses, the BBERF resides in the trusted non-3GPP access gateway, and the trusted non-3GPP network access gateway exchanges information with the PCRF via the Gxa interface. When a User Equipment (“UE” for short) roams, an S9 interface acts as the interface between a home PCRF and a visited PCRF, meanwhile, an Application Function (“AF” for short) providing service for the UE sends service information which is used to generate Policy and Charging Control (“PCC” for short) policy to the PCRF via a Rx+ interface.
A plurality of PCRF nodes exist in one Public Land Mobile Network (“PLMN” for short) of the EPS, and all the PCRF nodes belong to one or more Diameter domains (i.e., PCRF domain), and all the PCRFs in a same Diameter domain (i.e., PCRF domain) have same capacity. The connection of one UE to the PDN network is called as one IP Connectivity Access Network (“IP-CAN” for short) session. The PCC policy of one IP-CAN session is merely decided by one PCRF. In order to ensure all the PCEFs or BBERFs related to one IP-CAN session and the AFs which provide service for this IP-CAN session are all associated with the same PCRF, the EPS introduces one logical function means, i.e., Diameter Routing Agent (“DRA” for short), into each Diameter (PCRF) domain.
When the UE is to establish the IP-CAN session to one PDN, one PCRF is selected by the DRA for this IP-CAN session, the PCEFs, the BBERFs and the AFs related to this IP-CAN session are associated to the selected PCRF through the DRA. The PCEF, BBERF and AF establish the Diameter sessions with the selected PCRF, respectively, and the policy and service information, etc. for controlling the IP-CAN session are transmitted via these Diameter sessions. In order to ensure that the DRA associates the PCEF, BBERF and AF with one PCRF correctly, the DRA should save the related information capable of uniquely identifying this IP-CAN session and corresponding PCRF identifier or IP address, the information identifying the IP-CAN session includes the Network Address Identity (“NAI” for short) of the UE, the IP address of the UE, the Access Point Name (“APN” for short) through which the UE accesses the PDN, and so on. When the PCEF, the BBERF and the AF of the same IP-CAN session establish the Diameter sessions with the PCRF, the information is provided to the DRA, and the DRA may select the same PCRF for it by searching for the saved information. The information of the Diameter session established by the PCEF, the BBERF or the AF and the PCRF, for instance, the session identity of the established Diameter session, and so on, may be saved in the DRA, thus the DRA can know the Diameter session it manages for the IP-CAN session. The DRA may also select the same PCRF for all the IP-CAN sessions of the UE. When the Diameter session established by the PCEF, the BBERF or the AF and the PCRF is deleted, the PCEF, the BBERF or the AF will notify the DRA that this Diameter is deleted, and the DRA may delete the information (e.g. session identifier) of this Diameter session. When all the Diameter sessions managed by the DRA for a certain IP-CAN session are deleted, the DRA will delete all the information of this IP-CAN session. When the DRA selects a same PCRF for all the IP-CAN sessions of the UE, the DRA will delete all the information of this IP-CAN session after all the Diameter sessions managed by the DRA for this UE are deleted.
Currently, the EPS has three types of roaming architectures. The first type is home routed. FIG. 1 is a roaming architecture view of the home routed of the EPS. As shown in FIG. 1, the P-GW is in the home network, and is provided with IP service by a home network operator (i.e., the AF is in the home network). The second type is local breakout and the IP service is provided by the home network operator. FIG. 2 is a roaming architecture view of the local breakout and the home network operator providing the IP service. As shown in FIG. 2, the P-GW is in a visited network and is provided with the IP service by the home network operator (i.e., the AF is in the home network). The third type is the local breakout and the IP service is provided by a visited network operator. FIG. 3 is a roaming architecture view of the local breakout and the visited network operator providing the IP service. As shown in FIG. 3, the P-GW is in the visited network, and is provided with the IP service by the visited network operator (i.e., the AF is in the visited network).
The DRA can be realized specifically in the following three modes: (1) a Redirect mode, wherein when the PCEF, the BBERF and the AF send a Diameter session establish request message to the PCRF, this message is firstly sent to the DRA. If the DRA has not had any information related to this IP-CAN session yet, the DRA will select one PCRF for this IP-CAN session and feeds back the identifier or address of the selected PCRF to the sender; if the DRA has already had the information related to this IP-CAN session, the DRA feeds back the identifier or address of the corresponding PCRF to the sender. The sender sends the Diameter session establish request message to the selected PCRF after the sender obtains the address or the identifier of the PCRF; (2) a Proxy mode, wherein when the PCEF, the BBERF and the AF send the Diameter session establish request message to the PCRF, this message is firstly sent to the DRA. If the DRA does not have any information related to this IP-CAN session, the DRA selects one PCRF for this IP-CAN session and forwards the message related to this IP-CAN session to the selected PCRF; if DRA has already had the information related to this IP-CAN session, the DRA forwards the message related to this IP-CAN session to a corresponding PCRF, and the acknowledgement message of the PCRF is also forwarded to the PCEF, the BBERF or the AF via the DRA; and (3) a modification of the Proxy mode which is similar to the Proxy mode and different at: the DRA will also send the address of the PCRF to the PCEF, the BBERF or the AF when the DRA forwards an acknowledgement message fed back by the PCRF. Thereby, in subsequent message interacting, the PCEF, the BBERF or the AF can interwork directly with the PCRF without passing through the DRA.
Regarding the above mode (2), no matter it is the session establish message in the first place or the subsequent messages, they all pass through the DRA, thus, when the Diameter session is to be terminated, the DRA may analyze and obtain the indication for terminating the session carried in the message so as to delete the information of this session in the DRA. Regarding the above mode (3), when the Diameter session is to be terminated, it can be realized merely by that firstly a client sends a termination message to the DRA and then the DRA forwards the same to the PCEF. Regarding the mode (1), a problem yet to be solved is how the client deletes the information related to the session in the DRA when terminating the Diameter session with the PCRF, especially under the roaming scene. There is still no good solution at present for deleting the related information saved in the DRA when one Diameter session is terminated.